1. Field of the Invention
The invention relates to liquid purification or separation and to processes for separation. The invention also relates to a particulate material type separator such as a sand bed, including same with rehabilitation means such as a surface traversing type.
2. Description of the Prior Art
Artificial soil beds such as sand beds are known for use in septic systems, although uniformly such beds are employed for processing liquids as compared to solids, since the long term application of solids to such beds quickly leads to plugging. U.S. Pat. No. 4,039,451 to Smith teaches an artificial bed that receives liquids, which are allowed to percolate through the bed to a collection pipe under the artificial sand bed. U.S. Pat. No. 4,100,073 to Hopcroft discloses another sand filter bed for liquids, wherein the bed is contained in a liner for preventing loss of liquid other than through the intended discharge point. The teachings of both noted patents include the removal of solids prior to application of the material to the artificial bed and in this respect are in conformity with the customary treatment practices for waste materials.
The use of land for the disposal of waste products produced by industries, municipalities and agricultural generators is a potentially efficient and environmentally sound solution to the problem of waste disposal, but it also represents technical and environmental challenges. Large areas of land may not be available or may be prohibitively expensive. Climate and soil conditions may prevent allseason use of land, and groundwater may be polluted or the risk of such occurring may be considered to be potentially high because of the waste characteristics or loading rates with consequent risk to public health. As a result, the use of land application as a disposal medium is often rejected in favor of other methods that require significant capital expenditures, demand large amounts of energy and create negative impacts to the environment.
Revision of and the creation of new, more restrictive guidelines by state and federal agencies could potentially and seriously limit the use of land as a disposal media. Land disposal of liquid waste materials has been practiced for many years in the United States under a wide range of geographic, topographic, climatic and soil conditions. Most of the operations have been accomplished without monitoring the effect on the environment. With the increase in the use of land, criteria and guidelines have been prepared for such areas as site selection and management techniques. The issuance of permits to operate the majority of these types of facilities is now a mandatory requirement. The growth of land application and the data being collected, including research and development being generated on the potential environmental impacts has caused some concerns relative to safe operations under specific physical site constraints and the local environment.
The existing guidelines also include a requirement that the waste must be stabilized--chemically or biologically. The process of stabilization tends to reduce the pathogenic population in the waste and thereby to reduce the potential risk to public health caused by transmittal through the soil system and into the groundwater. The cost of the stabilization process is high in terms of both capital facilities and operation/maintenance expenses.
Little information concerning the movement and survival of viral pathogens through the soil via percolating water is available. Many potential problems are also associated with excessive concentrations of metals and other trace elements within the waste system.
A major factor in land application of wastes is the land itself, especially the upper horizons of soil in which plants grow. Injection of sludge into the soil has been practiced, as by supplying sludge to an injector moved by a tractor. A well engineered land injection operation must recognize the limitation of the soil and then design for maximum utilization of the assimilative capacity of a soil such as its filtration, biological degradation and absorption properties. The ultimate benefit derived from the purifying and assimilating capacity of a soil is the establishment of favorable plant cover. This inevitably depends upon three closely related factors: the triad of liquid sludge properties, land and soil properties, and plant nutrient requirements.
The environmental balance of a land application system is critical for a successful system with much of the anticipated results being nonpredictable under present circumstances. The potential unknown elements in land applications have caused concern to industries and municipalities in the use of this method of waste disposal. The present invention has been developed to eliminate environmental concerns and to provide a completely controlled atmosphere in which to dispose, potentially, both nonhazardous and hazardous waste material. In addition, the system can also provide a beneficial byproduct through the control of system loading rates and waste characteristics.